diff --git a/problems/0051.N皇后.md b/problems/0051.N皇后.md
index 5404b620..9cc84cf8 100644
--- a/problems/0051.N皇后.md
+++ b/problems/0051.N皇后.md
@@ -332,7 +332,7 @@ class Solution {
 
     public boolean isValid(int row, int col, int n, char[][] chessboard) {
         // 检查列
-        for (int i=0; i<n; ++i) {
+        for (int i=0; i<row; ++i) { // 相当于剪枝
             if (chessboard[i][col] == 'Q') {
                 return false;
             }